One of the known technologies for combining a plurality of images to obtain a high-resolution image is a pixel-shift super-resolution technology that achieves improved resolution by combining images photographed by relatively displacing the positions of an optical image and an imaging system. Specifically, the plurality of images photographed by relatively displacing the positions of the optical image and the imaging system are arranged while taking into account the amount of displacement in an image space having higher resolution than the photographed images, and the resolution is improved by performing an interpolation process, a repetitive reconfiguration process, and so on based on the image information. This technology is advantageous in that the resolution can be improved since aliasing (moiré) is removed as a result of combining a plurality of positionally-displaced images with respect to a subject that may cause aliasing to occur in a photographed image, such as a subject with a fine pattern.
However, the above-described technology is problematic in that artifacts, such as a ghost image, may occur in a region that involves movement of the subject. A technology disclosed in Patent Literature 1 is known for reducing such artifacts in a moving-object region.
In Patent Literature 1, a correlation amount is calculated between a plurality of images, and a combining ratio of the images is controlled based on the correlation amount. For example, of the plurality of photographed images, one image is set as a standard image and another image is set as a reference image. A difference between the standard image and the reference image is determined for each region, and a correlation amount relative to the standard image is calculated from the difference value. Control is performed such that the combining ratio of the reference image increases with increasing correlation and the combining ratio of the reference image decreases (i.e., the ratio of the standard image increases) with decreasing correlation. Accordingly, artifacts, such as a ghost image, caused by movement of the subject or by positional displacement are prevented from occurring.